still i m ignorent about the use of zoom assist button, and didnt use it. can u please inform me here how to use it? at last, thanks for sharing.

The top button where your left thumb falls when grasping the lens barrel helps you to find your subject when the lens in all the way out in its zoom range. When you press the top button, the lens automatically pulls in to reveal a wider angle of view. Place your subject right in the middle in the focus box in the wider view. Release the button and the lens automatically zooms back out with your subject now filling the screen. The amount of pull-back when you press the button can be adjusted in the "Display Area" setting in the menus. I have it set to Medium.